The West African Craton (WAC) is one of the five cratons of the Precambrian basement rock of Africa that make up the African Plate, the others being the Kalahari craton, Congo craton, Saharan Metacraton and Tanzania Craton. Cratons themselves are tectonically inactive, but can occur near active margins, with the WAC extending across 14 countries in Western African, coming together in the late Precambrian and early Palaeozoic eras to form the African continent. It consists of two Archean centers juxtaposed against multiple Paleoproterozoic domains made of greenstone belts, sedimentary basins, regional granitoid-tonalite-trondhjemite-granodiorite (TTG) plutons, and large shear zones. The craton is overlain by Neoproterozoic and younger sedimentary basins. The boundaries of the WAC are predominantly defined by a combination of geophysics and surface geology, with additional constraints by the geochemistry of the region. At one time, volcanic action around the rim of the craton may have contributed to a major global warming event.
The Birimian rocks are major sources of gold and diamonds that extend through Ghana, Côte d'Ivoire, Guinea, Mali and Burkina Faso. They are named after the Birim River, one of the main tributaries of the Pra River in Ghana and the country's most important diamond-producing area. Ghana and Mali are the second and third largest producers of gold in Africa, respectively.
The Birim River is one of the main tributaries of the Pra River in Ghana and the country's most important diamond-producing area, flowing through most of the width of the Eastern region. The river rises in the east of the Atewa Range, flows north through the gap between this range and the Kwahu Plateau, then runs roughly south-west until it joins the Pra. It gives its name to the Birimian rock formation, which yields most of the gold in the region. Ghana is the second largest producer of gold in Africa.
The Man Shield is a geological shield or craton in the southeast portion of the West African Craton. The shield is in part overlaid by gold-bearing Birimian formations.
The geology of Vietnam is divided into five structural blocks : Northeast (NE), Northwest (NW), Truongson, Kon Tum and Nambo. The NE block is a part of the South China plate, in which strata and igneous rocks have been found dating from the Early Paleozoic to the Quaternary. The NW and Truongson blocks are regarded as NW-SE trending Paleozoic folded systems filled with thick Paleozoic formations. Precambrian strata are widespread in the Red River Fault zone and Fansipan range in the NW block, and in the Kon Tum block. Archean rocks are found only in the Kon Tum block, which is regarded as a stable massif without Paleozoic sedimentary rocks. The Nambo block is covered with a very thick sequence of Cenozoic formations deposited in a continental rift. During the Mesozoic many such graben structures were formed and become basins for sedimentation. Igneous activity in Vietnam is divided into five episodes from the Archean to Quaternary. The most important impediments to the description and interpretation of geology in Vietnam are lack of reliable radiometric and structural data, and scarcity of good outcrops.
The geology of Togo is largely of gneisses and granitic rocks of Proterozoic age in the central and southern part of the country. These are overlain in the coastal zone by Cretaceous and Cenozoic sediments. The northern part of the country has a basement of Neoproterozoic metamorphic rocks and Paleoproterozoic granite. The south of the country is covered in sedimentary basins, covering 3,300 km.2 of land. The West African Craton is made up of crystalline structures, ranging in age from the Neoarchean to the Paleoproterozoic age. The North-Dapaong zone, which is located in the West African Craton, migmatites, gneisses, amphibolites, granodiorites and granites are commonly found. The Neoproterozoic Volta Basin contains sedimentary formations on the Birrimian bedrocks. These sedimentary formations are divided into two groups: an intra-tillite group and a supra-tillite group.
The geology of Burkina Faso is dominated by Precambrian rocks of the Guinea Rise, a dome of Archaean rocks, composed largely of migmatites, gneisses and amphibolites, over which lie the greenstone belts of the early Proterozoic age. The latter are metasediments and metavolcanics assigned largely to the Birimian Supergroup, a suite of rocks in which economically significant mineralization occurs. Pre-Birimian migmatites, gneisses, and amphibolites, located under the Birimian rocks, are the oldest rocks in the country. The Birimian deposits in the southwestern part of the country are typically divided between clastic and volcano-clastic formations.
The geology of Zimbabwe in southern Africa is centered on the Zimbabwe Craton, a core of Archean basement composed in the main of granitoids, schist and gneisses. It also incorporates greenstone belts comprising mafic, ultramafic and felsic volcanics which are associated with epiclastic sediments and iron formations. The craton is overlain in the north, northwest and east by Proterozoic and Phanerozoic sedimentary basins whilst to the northwest are the rocks of the Magondi Supergroup. Northwards is the Zambezi Belt and to the east the Mozambique Belt. South of the Zimbabwe Craton is the Kaapvaal Craton separated from it by the Limpopo Mobile Belt, a zone of deformation and metamorphism reflecting geological events from Archean to Mesoproterozoic times. The Zimbabwe Craton is intruded by an elongate ultramafic/mafic igneous complex known as the Great Dyke which runs for more than 500 km along a SSW/NNE oriented graben. It consists of peridotites, pyroxenites, norites and bands of chromitite.
The mining industry of Guinea was developed during colonial rule. The minerals extracted consisted of iron, gold, diamond, and bauxite. Guinea ranks first in the world in bauxite reserves and 6th in the extraction of high-grade bauxite, the aluminium ore. The mining industry and exports of mining products accounted for 17% of Guinea’s gross domestic product (GDP) in 2010. Mining accounts for over 50% of its exports. The country accounts for 94% of Africa’s mining production of bauxite. The large mineral reserve, which has mostly remained untapped, is of immense interest for international firms.
The geology of Guinea-Bissau is oldest in the east and becomes younger toward the west, with sediments from the past 66 million years nearer the coast. Some rock units in the northeast are as much as 680 million years old and throughout the geologic past Guinea-Bissau was influenced by the Mauritanide Belt orogeny and was submerged or partially submerged as a marine shelf or river delta for most of its existence.
The geology of Liberia is largely extremely ancient rock formed between 3.5 billion and 541 million years ago in the Archean and the Neoproterozoic, with some rocks from the past 145 million years near the coast. The country has rich iron resources as well as some diamonds, gold and other minerals in ancient sediment formations weathered to higher concentrations by tropical rainfall.
The geology of Ghana is primarily very ancient crystalline basement rock, volcanic belts and sedimentary basins, affected by periods of igneous activity and two major orogeny mountain building events. Aside from modern sediments and some rocks formed within the past 541 million years of the Phanerozoic Eon, along the coast, many of the rocks in Ghana formed close to one billion years ago or older leading to five different types of gold deposit formation, which gave the region its former name Gold Coast.
The geology of Cameroon is almost universally Precambrian metamorphic and igneous basement rock, formed in the Archean as part of the Congo Craton and the Central African Mobile Zone and covered in laterite, recent sediments and soils. Some parts of the country have sequences of sedimentary rocks from the Paleozoic, Mesozoic and Cenozoic as well as volcanic rock produced by the 1600 kilometer Cameroon Volcanic Line, which includes the still-active Mount Cameroon. The country is notable for gold, diamonds and some onshore and offshore oil and gas.
The geology of Ivory Coast is almost entirely extremely ancient metamorphic and igneous crystalline basement rock between 2.1 and more than 3.5 billion years old, comprising part of the stable continental crust of the West African Craton. Near the surface, these ancient rocks have weathered into sediments and soils 20 to 45 meters thick on average, which holds much of Ivory Coast's groundwater. More recent sedimentary rocks are found along the coast. The country has extensive mineral resources such as gold, diamonds, nickel and bauxite as well as offshore oil and gas.
The geology of Mauritania is built on more than two billion year old Archean crystalline basement rock in the Reguibat Shield of the West African Craton, a section of ancient and stable continental crust. Mobile belts and the large Taoudeni Basin formed and filled with sediments in the connection with the Pan-African orogeny mountain building event 600 million years ago and a subsequent orogeny created the Mauritanide Belt. In the last 251 million years, Mauritania has accumulated additional sedimentary rocks during periods of marine transgression and sea level retreat. The arid country is 50% covered in sand dunes and has extensive mineral resources, although iron plays the most important role in the economy.
The geology of Niger comprises very ancient igneous and metamorphic crystalline basement rocks in the west, more than 2.2 billion years old formed in the late Archean and Proterozoic eons of the Precambrian. The Volta Basin, Air Massif and the Iullemeden Basin began to form in the Neoproterozoic and Paleozoic, along with numerous ring complexes, as the region experienced events such as glaciation and the Pan-African orogeny. Today, Niger has extensive mineral resources due to complex mineralization and laterite weathering including uranium, molybdenum, iron, coal, silver, nickel, cobalt and other resources.
The geology of Sierra Leone is primarily very ancient Precambrian Archean and Proterozoic crystalline igneous and metamorphic basement rock, in many cases more than 2.5 billion years old. Throughout Earth history, Sierra Leone was impacted by major tectonic and climatic events, such as the Leonean, Liberian and Pan-African orogeny mountain building events, the Neoproterozoic Snowball Earth and millions of years of weathering, which has produced thick layers of regolith across much of the country's surface.
The geology of South Sudan is founded on Precambrian igneous and metamorphic rocks, that cover 40 percent of the country's surface and underlie other rock units. The region was affected by the Pan-African orogeny in the Neoproterozoic and extensional tectonics in the Mesozoic that deposited very thick oil-bearing sedimentary sequences in rift basins. Younger basalts, sandstones and sediments formed in the last 66 million years of the Cenozoic. The discovery of oil in 1975 was a major factor in the Second Sudanese Civil War, leading up to independence in 2011. The country also has gold, copper, cobalt, zinc, iron, marble, limestone and dolomite.
The geology of Senegal formed beginning more than two billion years ago. The Archean greenschist Birimian rocks common throughout West Africa are the oldest in the country, intruded by Proterozoic granites. Basins formed in the interior during the Paleozoic and filled with sedimentary rocks, including tillite from a glaciation. With the rifting apart of the supercontinent Pangaea in the Mesozoic, the large Senegal Basin filled with thick sequences of marine and terrestrial sediments. Sea levels declined in the Eocene forming large phosphate deposits. Senegal is blanketed in thick layers of terrestrial sediments formed in the Quaternary. The country has extensive natural resources, including gold, diamonds, and iron.
The geology of Cambodia is the study of the nation's rocks, minerals, water and landforms. Cambodia's ancient geologic history in the Precambrian is poorly understood. The region experienced tectonic activity and low-grade metamorphic rock formation throughout the Paleozoic, which a shift to marine conditions and fossil formation during the Permian and through much of the Mesozoic. Few rocks remain from the Cenozoic. Cambodia has comparatively few natural resources, although there is bauxite formed from laterite weathering, as well as phosphorite, iron, gems, limestone and other materials.
